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Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
So I met Dyno Don yesterday. Super nice guy and some very cool 3rd gen stuff going on in there. I picked up an 88 L98 B2 (iron heads) from a GTA from him and promptly dropped it off at a machine shop. If it turns out fine, it will be bored 0.030 over and refreshed. As long as I'm doing this, I want to put in forged pistons since I believe they are much tougher than hypers and I may want to add a little NOS in the future. The engine will be otherwise stock (bigger cam) but refreshed.
Don suggested I go with a piston from a 90-91 which bumps the compression ratio from 9.3 to 9.6.
I did some looking around on Summit Racing and found these four that appear to fit the need. I'm looking for affirmation or otherwise!
Not sure what you had in your "compare", as the link doesn't work.
I suggest strongly NOT trying to buy them as "replacement" for a specific "application", such as you describe. They pretty much DON'T come that way.
Whatever you pick: NOT Speed-Pro. Those are the old TRW line. They are basically replacement truck pistons; heavy, old-style, and they add the .020" of "rebuilder" deck clearance, which you DO NOT UNDER ANY CIRCUMSTANCES want. ACTUAL MEASURED compression height, as opposed to "spec", "designed to fit", "for motors with", etc., should be 1.56", NOT 1.54". Most likely this will mean Wiseco, Ross, JE, SRP, or other similar products. True racing parts, not "replacement". You don't have to go all-out or anything, just, make sure the pistons come up to the top of the deck at TDC. Keith Black & ICON might be suitable choices as well, I don't know for sure.
Don't buy the cheeeeeeepest thing you can find that says "forged" in the ad copy.
Make ABSOLUTELY SURE the bore & hone are done with a deck plate. The act of bolting on the heads distorts the block, and if the cyls are "round" without the heads, it is ABSOLUTELY CERTAIN that they will NOT be round when the heads are installed.
And, have the deck cut to "square". A stock block is usually as much as .005" out from side to side, int to exh, and/or front to rear; and often MUCH more than that. Nominal stock deck height is 9.025" and is usually randomly and unevenly greater than that, but the rotating assy (½ the stroke, plus rod length, plus compression height), is nominally 9.000", meaning you already start out with .025" of unwanted deck clearance. You can have up to that much metal knocked off without worry.
Similarly, you want the rods to all be as close as possible to 5.700" long, and within a gram or 2 of the same weight at both ends. You can do the balancing yourself easily enough.
And, once ALL THAT is finished, have the rotating assy balanced by a competent shop. They'll need the crank rods & pistons, and maybe the rings or at least the measurement of the weight of a ring set. DO NOT allow your flex plate or flywheel and your crank damper to be in the same shop at the same time!!!! Have the rot assy balanced to the STOCK spec, then if you want, have those other parts balanced SEPARATELY to their STOCK specs. NOT, balance them all together; that's a shortcut some shops take to avoid doing it RIGHT, and leads to the problem where if you ever have to change ANY ONE part, the whole shebang is then out of balance. DO NOT let them talk you into doing otherwise.
ACTUAL MEASURED compression height, as opposed to "spec", "designed to fit", "for motors with", etc., should be 1.56", NOT 1.54". Most likely this will mean Wiseco, Ross, JE, SRP, or other similar products. True racing parts, not "replacement". You don't have to go all-out or anything, just, make sure the pistons come up to the top of the deck at TDC. Keith Black & ICON might be suitable choices as well, I don't know for sure..
Totally agreeing with Sofa. ACTUAL MEASURED is the important part people often skip. I personally have Icons in my 92. They are pretty high quality especially per dollar. I think mine are these exact ones. Key word "think". https://www.summitracing.com/parts/u...make/chevrolet Just an example that Icons are a decent choice. Pick whatever manufacturer you prefer, just don't neglect compression height. On mine, my measured compression on a 083 headed 355 was something 9.9xx, if I recall correctly. It's been like 7 years since I put it together. Make sure to do your own math.
Whatever you pick: NOT Speed-Pro. Those are the old TRW line. They are basically replacement truck pistons; heavy, old-style, and they add the .020"..., should be 1.56", NOT 1.54". .
Perhaps not all Speed-Pro are created equal. Two things with respect to that statement though.
1) That PN is more than 10 years old (from my 2nd time around 1st build) and
2) They're hypereutectic.
And the 3rd selection has thinner rings. I have been told to avoid the thinner rings on a typical street build. I was told the thicker rings promote sealing with more drag. I'm not saying that's the bold truth. Just what I have been told. Others with more build experience may have more input on that.
Last edited by aliceempire; 08-18-2019 at 06:55 PM.
aliceempire, I think the third choice Icons are the same ones in your link. And 5/64 is thicker than 1/16 (by another 1/64) so I'm guess that's actually a good thing?
And skinny z so I need to stick with the 1.565 compression height?
Sofa, so a deck plate is like having the cylinder head bolted down to the block and then honing? This hones the bore the way the block will be distorted with the heads installed?
Last edited by Tootie Pang; 08-22-2019 at 11:08 PM.
And I would also point out that the Chevrolet Power 5th edition (published in 1984), states on page 1-4:
"On rebuilds, bores should not be rehoned unless absolutely necessary if maximum power is to be achieved from minimum ring friction."
GM doesn't hone cylinders in cases where pistons must be replaced under warranty and neither does any other manufacturer that I'm aware of.
Honing is an old wives tale. Pure and simple. If it does need to be bored then follow the sound advise to only have this performed with a bore plate. But I think you will find the bores are just fine as-is. Boring it oversized will only remove material making the bores unnecessarily thin and prone to future cracking - especially if NOS is used. I would avoid if possible.
The comment above about avoiding thin rings - that goes along with this. The issue is using too rough of a surface finish and causing the rings to overheat and lose their tension during seating. Thin rings are GOOD for performance (look at the LS engines) as they provide much better sealing and much lower friction. If the proper surface finish is used (a good condition used bore is ideal in fact) they seat and work very well.
DO line hone the main journals so you can use a single set of bearings. GM picked bearing inserts as the engines were assembled and it's highly unlikely you would be able to purchase a single bearing set and get proper clearances. Also line hone the cam line and have the machine shop properly install the cam bearings. Have the deck's trued up and surfaced properly for use with an MLS gasket.
For pistons - I would look at JE. We use JE or Wiseco and both have been excellent quality. Stay away from the parts store branded Chinese stuff. That's a terrible idea. Better to just put the originals back in if that's the plan.
And skinny z so I need to stick with the 1.565 compression height?
If you're using a stock length 5.7" rod, yes.
As for the rest, there are more experienced minds than mine that have weighed in on the other questions.
That said, a machine shop that's performance orientated and not just a rebuilder will most certainly use a deck plate for their machining operations. And yes, the torque plate simulates the stresses that a bolted on cylinder head would impart on the roundness of the bore.
As for using a thin ring pack, again it was pointed out that this is what the LS engines use. And it would be a fair bet that ALL of the OEM's have incorporated this into their engine packages. These days their focus is on engine efficiency. And reducing friction increases that efficiency. As with the deck plate, a competent machine would know exactly the type of surface finish required when using the thinner rings so your faith would have to go with them. As for nitrous, well, thick or thin rings, forged or cast pistons, and all of the rest is user beware. You can burn a hole through anything if you try hard enough.
Instead of crowdsourcing an engine build here on TGO, how about you work with a good performance-oriented machine shop so they can properly inform you and spec the build properly?
Instead of crowdsourcing an engine build here on TGO, how about you work with a good performance-oriented machine shop so they can properly inform you and spec the build properly?
^^^^ THIS.
While everybody has to start somewhere if they plan to build engines, your best bet is to follow the advice of the guy who is doing all the machine work and/or the assembly.
While everybody has to start somewhere if they plan to build engines, your best bet is to follow the advice of the guy who is doing all the machine work and/or the assembly.
Eh - machinists aren't perfect, and they get to charge for each operation you "need" - so it follows that most machinists will sell every machining operation they are competent performing.... because profit. Using the premis that "it won't hurt to clean it up a little - it will be better!" They are very good at finding bad reasons to do dumb things with other peoples money - and they convince even themselves that a little "cleanup" here and there is for the best. It is usually just burning money needlessly. My machinist still tries to sell me overbore's and honing on engines I know more about than he does. You see - machinists view the world through a micrometer. They don't actually put the engines in cars and stick them on a dyno. Most of them anyway. They see numbers in their notebook and want to make the whole mess back to "like new" specs - which is not always necessary, and often it's not what you want for a performance build anyway as the OEM's are looking to hit specs that are for economies of scale and to pass regulations without undue stress on the warranty.
GD
Last edited by GeneralDisorder; 08-19-2019 at 12:52 PM.
Eh - machinists aren't perfect, and they get to charge for each operation you "need" - so it follows that most machinists will sell every machining operation they are competent performing.... because profit. Using the premis that "it won't hurt to clean it up a little - it will be better!" They are very good at finding bad reasons to do dumb things with other peoples money - and they convince even themselves that a little "cleanup" here and there is for the best. It is usually just burning money needlessly. My machinist still tries to sell me overbore's and honing on engines I know more about than he does. You see - machinists view the world through a micrometer. They don't actually put the engines in cars and stick them on a dyno. Most of them anyway. They see numbers in their notebook and want to make the whole mess back to "like new" specs - which is not always necessary, and often it's not what you want for a performance build anyway as the OEM's are looking to hit specs that are for economies of scale and to pass regulations without undue stress on the warranty.
GD
What you describe is the difference between a bad shop and a good shop, nothing more. A good performance shop will know what the microns mean in regards to performance and real-world application.
Working directly with the person doing the machine work to spec the build is the wisest thing someone could do as their first time around. Gathering a bunch of second-hand knowledge from forums and hoping for the best is a recipe for disappointment, imo.
Eh - machinists aren't perfect, and they get to charge for each operation you "need" - so it follows that most machinists will sell every machining operation they are competent performing.... because profit. Using the premis that "it won't hurt to clean it up a little - it will be better!" They are very good at finding bad reasons to do dumb things with other peoples money - and they convince even themselves that a little "cleanup" here and there is for the best. It is usually just burning money needlessly. My machinist still tries to sell me overbore's and honing on engines I know more about than he does. You see - machinists view the world through a micrometer. They don't actually put the engines in cars and stick them on a dyno. Most of them anyway. They see numbers in their notebook and want to make the whole mess back to "like new" specs - which is not always necessary, and often it's not what you want for a performance build anyway as the OEM's are looking to hit specs that are for economies of scale and to pass regulations without undue stress on the warranty.
GD
That's not been my experience (problems with machinists/paying for work not deemed necessary), but other than when I was a dealership mechanic, I've only ever dealt with two shops, both of which only did/do performance work. Never a complaint, never an issue.
Of course a beginner doesn't yet know what he doesn't know.
What you describe is the difference between a bad shop and a good shop, nothing more. A good performance shop will know what the microns mean in regards to performance and real-world application.
Working directly with the person doing the machine work to spec the build is the wisest thing someone could do as their first time around. Gathering a bunch of second-hand knowledge from forums and hoping for the best is a recipe for disappointment, imo.
I understand what you are saying, and in a perfect world that would be the case. Unfortunately it's not as cut and dried as all that. As a performance shop owner that builds engines (which the customer must be satisfied with, and perform as promised) but necessarily has to outsource the machine work (I simply don't have the equipment or the space to house it - we have a chassis dyno instead) I see a lot of machine work - good, bad, and unnecessary - that's performed at other shops - often the unnecessary machine work (especially in the case of honing) is the REASON it ends up in my hands - because the engine doesn't perform as promised or it uses a ton or oil, slobbers blow-by everywhere, or whatever. You talk to the previous shop and they blame the machinist - who of course blames the shop and customer for improper break-in or other mishandling. It's a viscous circle of blame and unhappiness. I see shops screw up a perfectly good engine with a bottle-brush hone job - ALL THE TIME. It's ridiculous.
Honestly - if you are going to take the block to a machine shop and just let them go hog-wild with it and do "whatever they say" without question - it will ALMOST ALWAYS be cheaper and easier to just buy a crate engine.
Well I was getting ready to go over there and ask him to use a deck plate but now I'm wondering if I can/should do minimal work. This is going to be essentially a stock motor so if I don't need to hone, I don't want to. I am working directly with the shop owner and machinists. It's been a long time since I did a motor and I always like to start with the collective wisdom that exists (here for example).
For my needs, stock 350, minimal cost/drama, recreational/low mileage use, it sounds like I shouldn't do anything that isn't needed. This logic agrees with the shop owner who said he would take everything apart and check it over before anything else. They do performance stuff, but they are not performance oriented. I trust them and will communicate that I want to do the minimum recommended.
What you all say would be the minimal work that should be done while it is out of the car? Assuming everything is right- replace rings, bearings, pistons?
And the 3rd selection has thinner rings. I have been told to avoid the thinner rings on a typical street build. I was told the thicker rings promote sealing with more drag. I'm not saying that's the bold truth. Just what I have been told. Others with more build experience may have more input on that.
Read not too long ago thin rings conform to the bore better and thus seal better. OEM's use thinner rings these days like in the vortec 350. They also reduce drag and make a bit more HP
Align hone (absolutely most critical IMO), square the decks, check the cam line. Polish the crank, resize the rods. New bearings (cam, crank, rod) and rings. Run it. Open the ring gaps up if you plan to NOS it. The cylinder walls concern me very little unless they are seriously wacked or heavily scored - at which point it has to be bored so it's basically scrap if you ask me - you can buy a Vortec complete pull out for about $250. But you MUST have .002" plus or minus a couple tenths on the mains and rods, and the thrust needs to be within spec.
Read not too long ago thin rings conform to the bore better and thus seal better. OEM's use thinner rings these days like in the vortec 350. They also reduce drag and make a bit more HP
Even the Vortec rings are quite thick compared to modern rings.
I think that motor had a broken ring land (lot of blow by)
Ah interesting. We deal with broken ring lands all the time on the Subaru turbo engines. They *usually* don't hurt the cylinder walls - 95% of the time we just slam in some new forged slugs and run them. With forged pistons they NEED to be fit looser due to the higher density of the forged alloys (2618 is mostly what run) and so clearance ends up being *less* critical with forged slugs - the tolerances will already be wrecked when cold.
Funny - I just ordered a set of JE rings for a 4" bore Subaru motor this morning and noticed they were 1.2, 1.2, and 2.0 in the description and thought about this thread..... Which is stock for this engine also - not actually thinner than stock even though they are going on Forged JE replacement pistons.
Interesting to learn. I wonder why use or manufacture the wider rings anymore.
The Small Block Chevy aftermarket is HUGE. Billions of $ a year. People still buy this stuff - DIY mechanics, and shops doing stock rebuilds, etc. But new engines are not using them as engineers have moved away from them. Thinner rings conform better, seal better and faster, and allow more material in the piston to support them. They also present a smaller area to the wall and this creates less friction - less heat, less wear, and increased economy and power.
If I were buying pistons, I'd get ones that take thinner rings.
Part of the problem with "I've always heard" and "everybody says" and stuff like that is, lots of that stuff is A HALF CENTURY OLD, or more. Granted, some things never change; but some DO. And it's wise to keep an open mind to such things. Ring thickness is one such thing. The reason the ring mfrs make thick ones, is because PEOPLE STILL BUY THEM; and the reason they buy them is, DINOSAUR BRAIN. Think of the Neandertal tool technology: almost totally unchanged for 100,000 years. Not what I would consider the hallmark of intelligence.
Re-evaluate what you think you know every once in awhile.
I agree with the comments about leave the bores alone if they don't need attention. Back in the day (one of the things you "always hear") nobody in his right mind would try to put new pistons into old bores. It was one of the surest recipes for building a total POS. We used to call old 327s and 283s in particular, "Powerglided"... there would be a .015" OR MORE step at the top of all the bores. We blamed it on the transmission. Turned out once the T-350 and the Q-Jet became common, the problem wasn't that AT ALL; it was the old 2G 2-bbl carb. A car with a Q-Jet and a PG would develop less than ¼ the step on the bore that a 2G/350 car would. Modern EFI has taken that even farther: you can pull apart motors that have 200,000 miles on them and still see the cross-hatch in the bores.
So if your block doesn't NEED a bore job, DON'T!!! Buy std bore pistons and RUN IT. Use narrow rings like LS motors, good pistons with the full compression height as described above, and have your block's decks cleaned up to eliminate extra deck clearance. Align-honing is a good idea too, or at the very least, checking the bearing bores with a bore mic (a regular mic won't give you accurate enough measurements to be useful) to see if they are all the same size, and if so, what that size is.
Sofa is so right in so many ways. I deal with this EVERY DAY and I have customers walking in telling me "they saw" and "they heard" and "my friend says" and all manner of other foolishness. Most of it is wrong or seriously lacking. It's VERY hard to differentiate actual worthwhile information from the sea of noise that is the internet. Unfortunately there is precious little actual real world data coming in to the internet about this stuff because people like me often keep their hard-won experience and knowledge to themselves - considering it "proprietary information". I'm not real concerned about telling people how to do the job the right way - there's plenty that don't have the time or inclination, some that don't want to invest in the tooling when they find out what the "right way" tools cost, and a large number that try but end up screwing it all up and towing it to me anyway. There are nuances to assembling engines that we have learned through repetition - some that I'm only faintly consciously aware of I'm sure - and I don't always remember to impart all that information unless specific targeted questions are asked. So as with anything - take this information for what it's worth - which is exactly equal to what you paid for it.
So I swung into the shop today and he had taken the heads off and cleaned up the parts. He said it all looked good so far but recommended a .02 or .03 bore and hone. He showed me some streaks along the side of a couple bores. Even though it felt smooth, he said that happens when the piston gets too hot and are probably hard spots. He said if it's round, I don't have to bore, but he said as long as its opened up, might as well. He also said he could use a deck block but in his experience, for this build, he doesn't think it is necessary. He said these blocks are pretty stout. So I'm thinking hyper pistons might be just fine. I'm looking at the two options below.
Regardless of what he says - a few vertical scratches in a cylinder aren't going to do squat. Don't buy into that line of BS. Especially if he wants to "wing it" without a bore deck plate. That's just stupid.
If they look good other than a few minor vertical scratches - run the bores as-is. If you MUST buy pistons, get JE or WIseco. Again DON'T screw with Chinese garbage. It's NOT WORTH IT.
I've warned repeatedly not to listen to some "machinist" that wants to bore a perfectly good cylinder. I really don't know what else you want here? It's foolish - especially with no bore plate. You WILL ABSOLUTELY have a worse product than if you just left it alone.
Clevite bearings. Hastings rings - regular cast iron. If you buy pistons they will come with rings.
Typical machinist - "Might as well pay me more while I have it apart! I mean hey - it's only YOUR money and soon to be MY money so hell yeah! Might as well"
GD
Last edited by GeneralDisorder; 08-22-2019 at 11:41 PM.
I tried to find a 4.000 bore shelf kit for JE or Wiseco but neither list one. You will have to call them and make a special order. Save the money on doing the (wrong) machine work and put it toward nice 4.000 pistons. Or, if the pistons in the engine are good, slap in some Hastings cast iron rings, open up the gaps for your NOS and run it. A basically stock L98 build with a 150 shot isn't going to break the pistons unless you do something stupid. Ever watch Engine Masters? They took a used 70's 350 small block and on the Dyno they threw NOS at it till a piston failed and it took till about 700 HP to blow it.
"A few little scratches" won't really bother anything, in the big picture. THINK: even with a fresh bore, in a few k miles, you'll have new ones of those anyway. What good does it do to spend money on something that will just go right back like it was? I'm reminded of a friend of mine who used to detail his car, he was so **** about it that he would take a rag and wipe his wheel wells out to get them all shiny, and then the first thing he did next, was drive down his driveway through his wash water and mud at the curb, and splash mud all back up in his freshly wiped wheel wells. What good did all that wiping do? Same principle here: there is DEFINITELY a "good enough" level. Anything past that is a waste.
JE and the others only charge around $50 extra for custom pistons, compared to shelf. Worth every penny to get EXACTLY what you want.
Question here and one I know the answer to but it's worth asking anyway. Before we trot off to the parts store for this piston or that piston, shouldn't we (or in this case the machinist) actually measure the bores to determine if they are round? Or tapered? Or square? Seems to me that's the 1st logical step and yet the machinist or the OP has not brought that little detail to the surface.
Prior to having one of my 1st performance engines built (in a long long time), after dropping it off, I received a report regarding the condition of the engine and recommendations on how to proceed. Even though mine was a very pedestrian build (10:1 hypereutectic flat top pistoned Vortec headed 350 with a 70's vintage standard bore block with zero miles) they treated me much the same as the guy getting his Pro Stock engine built. Professional shop. Professional service.
If you can see the cross-hatch with your eyeball and there's no ring ridge..... what's measuring going to tell you? Any insignificant out of round-ness may go away with the heads torqued in place. You would need to bolt on a torque plate to take an accurate measurement and you will only find what you already knew if you can see cross-hatch.... it's going to be a decent bore with mild ovaling, and some slight taper but nothing to be concerned about. That's how they always are.
The factory cross-hatch is, at most, a few thou deep. So if it's still there - what does that tell us about the wear? All you need to do is use some critical thinking skills.
A question worth asking then because the answer was worth reading. Thanks GD.
I'm thinking along the lines of my own build I suppose. I don't have a full crosshatch as I've seen the thrust side quite shiny in comparison to the rest of the cylinder. No significant ridge though. This a well worn carbed application and this block has about 50 000 miles on it and probably the equivalent amount of gasoline washed down the cylinder walls as well.
For sure - carbs are THE biggest killer of engine longevity. Fuel washing of the cylinders due to poor cold-start enrichment control (better with the more advanced factory carbs like the Q-jet), and the fuel dilution of the engine oil makes for a powerful combination of wear-acceleration. Carbs are THE major reason that it was "conventional wisdom" prior to the late 1980's that a car was "good for about 100k miles" and then the drivetrain was basically worn out. Poor quality oils didn't help either, and the conventional wisdom itself was self-fulfilling in that people stopped maintaining cars that had over 75k miles. They just ran it till THE END - which was usually when it started smoking too badly to ignore and became a nuisance to the neighbors, and drank oil like it drank gasoline.
I remember very well visiting the scrap yards back in the late 70's and 80's and checking odometers to determine what good parts I might find. Finding something north of 100-120k miles was a rarity. Often rust would outpace the drivetrain but typically, with the exception of the incredibly robust GM differentials of the day, the drivetrain was toast first. Quick! Grab those fenders and doors before someone else does! Chances were, the SBC was long gone for the local circle track or drag racer's stockpile anyway.
Thanks to Tootie Pang for the loan of the thread.
The SBC is just more tolerant of abuse than other designs of the 1950's. Thus their popularity for the circle track, etc. I have a '70's van engine in my '69 GMC truck that's just shouldn't even run anymore - but it does. And runs decent even. It's so worn that some of the rockers have blown out their cups and fallen over into the head. I've just thrown on a $5 rocker a couple times now and it just wont die! It smokes a little on startup, and I when I pulled the intake not long ago there was at least 5 Lbs of hard carbonized oil and leaking exhaust from the gaskets in the valley. I use the cheapest oil I can get in it..... I can't seem to kill it and I wouldn't even mind laying it to rest! I have replacements for it. But it's just a utility truck so I can't justify the labor if it's still running OK.
So it sounds like if I'm going to have it bored and honed at all, use a bore plate. He has one and can use it. Otherwise, if everything is round, just re-ring it?
And how about these Wisecos? They are +7cc. Won't that lower my compression ratio?
Cool. 1/4 point for 2cc's? What are the stock pistons? I was advised to try to bring it to 9.6:1 like the 1991 5.7s Maybe I can go a little higher than that just because? 10:1? 10.5:1?
So by my reckoning, the thread says factory pistons are +12cc, so if these are +7cc then I lose 5cc with these Wiseco pistons and gain 0.25 CR for every two cc or 0.125 CR for each cc . And 0.125/cc x 5cc = +0.6 CR for 9.3 + 0.6 = 9.9 CR ?
Last edited by Tootie Pang; 08-24-2019 at 02:36 PM.
Time to figure out what your actual compression ratio will be I guess.
You have the block at the machine shop correct? The advice has been to get it decked, etc. Decking will change the installed height of the piston relative to the deck. So, you need that value before you can zero in on the actual number. While 2 cc is worth a 1/4 point (in and around the 9-10:1 range), the piston down the hole value may have greater impact. Same as head gasket thickness.
So:
Piston dish volume,
Piston to deck clearance.
Head gasket thickness (and diameter).
And the usual bore and stroke values.
The you can crank out a number.
It'll probably come out here that there should a specific quench to target as well. Arguably as important to making power without detonation as the compression ratio.
You seem to be in the perfect spot, the block at the shop before anything gets done, to direct how the build progresses. Given that they're not a performance orientated shop, this sort of stuff might get you better results if can give a little direction.
Make sense?
FTR:
If the stock deck is maintained and the piston below deck is .025" (an accepted OEM value), and the shop throws on the typical .040" gasket, you might get 9.:1 (as an example). Get the block decked to the piston being .014" down (as mine is) and use a .026" gasket (as I have) and it adds another 1/2 point to the CR.
Makes the piston choice less important doesn't it?
Awesome SkinnyZ. Thanks. Yes makes perfect sense. I’m actually going to pickup the block in pieces and assemble the motor with my son. I am planning on buying the parts so I will be sure to get the good gaskets.
If the head is decked and the block is decked with a proper surface finish, you can use an MLS gasket. I used the stock Vortec pistons, and just cleaned up the decks and heads but used a 0.015 MLS gasket. Same basic effect as doing a zero deck and a 0.040 gasket, but without losing block material. Of course it depends greatly on how much material has to come off the decks to get them true. Being I started with a Vortec that already had higher static compression I didn't need to bring it up much but I'm of the school that I want the head as close to the block as possible and the gasket as thin as possible for rigidity, and to present the smallest gasket cross section possible to the combustion process. Because Nitrous and prochargers and things.
For whatever reason, I've never liked the zero deck. I guess it's because once you go that far, you don't have the option to do it again should something happen that needed it.
I came into mine needing about ten thou to clean up the old 70s block and that put the pistons .014" down. That played perfectly in the Victor Reinz/Cometic/Clevite/Etc 5746 .026" Graphite/Nitroseal head gasket. Result was .040" quench.
An interesting point about NOS and boost regarding keeping things tight though. At my power levels I doubt I ever approached the limit of the head gaskets but then again I never tried a 150 shot either. We DID do that on one the "fleet" hotrods with a ZZZ crate 350and Edelbrock heads but we hardly punished that thing with seasons of racing. Just recreationally...
Exactly. I only remove material if absolutely necessary. Engine blocks live and die by their strength and their ability to dissipate heat. The goal is to start with an engine in decent shape, like a good condition L31 Vortec, and make it better. "Better" does not mean removing material just for the hell of it.
Regardless of what he says - a few vertical scratches in a cylinder aren't going to do squat. Don't buy into that line of BS. Especially if he wants to "wing it" without a bore deck plate. That's just stupid.
If they look good other than a few minor vertical scratches - run the bores as-is. If you MUST buy pistons, get JE or WIseco. Again DON'T screw with Chinese garbage. It's NOT WORTH IT.
I've warned repeatedly not to listen to some "machinist" that wants to bore a perfectly good cylinder. I really don't know what else you want here? It's foolish - especially with no bore plate. You WILL ABSOLUTELY have a worse product than if you just left it alone.
Clevite bearings. Hastings rings - regular cast iron. If you buy pistons they will come with rings.
Typical machinist - "Might as well pay me more while I have it apart! I mean hey - it's only YOUR money and soon to be MY money so hell yeah! Might as well"
So if the bores are good just stick with stock sized new wiseco pistons? Or even the OEM pistons? Should I do any prep to the bores for the new hardware?
Also, what a good streetable but fun CR? 10-10.5? Need to pass smog too.
08-18-2019, 11:20 AM
